JPH0753330B2 - Lift table - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a table used for a table and the like of a tatoba measuring instrument and a machine tool, and more particularly to a lift table for driving the table up and down by a screw feed mechanism.

(Prior Art) Conventionally, there is a device that uses a screw feed mechanism as a device for moving up and down a table on which a workpiece is placed for machining the workpiece, measuring dimensions, and the like. That is, the table is movably supported on the fixed bed through a screw feeding mechanism. The screw feed mechanism is composed of a vertically extending screw shaft and a nut screwed to the screw shaft. The table is fixed to the upper end of the screw shaft, and the nut is rotatably attached to the fixed bed side. . Then, the rotary drive source is operatively connected to the nut, and the nut shaft is rotated to linearly move the screw shaft in the up-and-down direction so that the table can be moved up and down.

In such nut-driven type, it is necessary to make the screw shaft movable in the axial direction and fixed in the rotating direction.A spline groove is provided at one end of the screw shaft separately from the screw groove, and a fixed bed is provided. It is known that a bearing fitted to the spline groove is provided.

Further, it is necessary to provide a transmission mechanism such as a worm and a worm wheel in order to rotationally drive the nut by the rotary drive source.

(Problem to be Solved by the Invention) However, in the case of the above-described conventional technique, in order to fix the screw shaft in the rotational direction, a spline groove is provided at one end of the screw shaft separately from the thread groove forming region. As a result, the overall length of the screw shaft becomes long, leading to an increase in the momentum device configuration. Further, when an unbalanced load or the like is applied to the table and a moment load acts on the screw shaft, there is a problem that the supporting rigidity is low because the only portion that supports the moment load is the engaging portion with the nut. .

Furthermore, since the transmission mechanism is interposed between the rotary drive source and the nut, it is difficult to perform precise positioning due to play of the transmission mechanism and the operation response is poor.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is a compact that has high support rigidity against bending moment, can be accurately positioned, and has excellent operation response. To provide a simple lift table.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a table is movably supported on a fixed bed via a screw feeding mechanism, and In a lift table having a screw shaft extending in the direction of which the upper end is fixed to the table, and a nut rotatably attached to the fixed bed side and operatively connected to a rotary drive source. While providing a hollow hole that opens, fix a spline shaft that can be axially movably inserted in the hollow hole of the screw shaft to the fixed bed, and for the sliding in the hollow hole of the ball screw shaft, the spline shaft moves in the axial direction. Is provided with a bearing that is movable and engages in a fixed state in the rotation direction, fixes the non-rotating portion of the rotary drive source to a fixed bed, and directly connects the rotating portion to a nut.

It is desirable that the spline shaft and the bearing portion are fitted through a large number of balls, and it is effective that the balls are in angular contact with the spline groove formed in the spline shaft and the bearing portion.

Also, it is desirable to interpose a large number of balls between the screw shaft and the nut, and preload is applied to these balls by shifting the phase of each thread groove on the nut side and the screw shaft side. Is preferred.

(Operation) In the lift table having the above configuration, when the nut is rotated by the rotary drive source, the screw shaft is held in a fixed state in the rotational direction by the spline shaft into which the bearing portion of the hollow hole fits, and the screw shaft is fixed to the spline shaft. Along the vertical direction, the table is moved up and down. The height of the table can be reduced by inserting this spline shaft into the hollow hole of the screw shaft.

When a moment load is applied to the screw shaft due to an eccentric load acting on the table, the moment load is doubly supported by the nut supporting the screw shaft outer peripheral side and the spline bearing portion supporting the inner peripheral side.

Furthermore, the nut is driven directly by the rotary drive source,
There is no play between the rotation drive source and the nut.

Also, if balls are placed between the spline shaft and the bearing, and further between the screw shaft and nut, the table can be moved easily, and by applying a preload to the balls, the load The additional capacity is increased, rattling at the time of forward / reverse rotation and starting / stopping is eliminated, and responsiveness is improved.

(Example) Below, this invention is demonstrated based on the Example shown. 1 to 7 showing a lift table according to an embodiment of the present invention, 1 denotes the entire lift table,
In general, it is composed of a fixed bed 2 and a table 4 which is supported on the fixed bed 2 via a screw feed mechanism 3 so as to be vertically movable.

The fixing bed 2 is a base having a substantially square shape, and bolt holes 5 for mounting and fixing are provided at four corners thereof. This fixed bed 2
The screw feed mechanism 3 provided above is protected by a cap-shaped hollow outer cover 6.

The screw feed mechanism 3 includes a ball screw shaft 7 extending in the vertical direction.
And a ball nut 9 screwed onto the ball screw shaft 7 through a large number of balls 8 ,. The ball screw shaft 7 is a thick-walled cylindrical member having a hollow hole 10 formed therein, and a spiral screw groove 11 is provided on the outer peripheral surface thereof over the entire length. The table 4 is integrally fixed to the upper end of the ball screw shaft 7 by a plurality of fixing bolts 12, .... The table 4 has a disk shape, and its outer diameter is set to be substantially the same as the outer diameter of the outer shape cover 6.

On the other hand, a ball spline shaft 13 is inserted into the hollow hole 10 of the hollow ball screw shaft 7 coaxially with the ball screw shaft 7 so as to be relatively movable in the axial direction. The lower end of the ball spline shaft 13 is fixed to the fixed bed 2 via a fixing bracket 14, and the middle portion thereof is a hollow hole 10 of the ball screw shaft 7.
The spline nut 15 as a bearing portion provided on the above is fitted in a state of being movable in the axial direction and being fixed in the rotating direction.

The ball nut 9 is directly driven by a servo motor 16 as a rotation driving means.
Is attached so as to surround the outer circumference of the ball screw shaft 7.

The ball 8 interposed between the ball screw shaft 7 and the ball nut 9 has an infinite circulation path of the ball 8 formed by, for example, a return tube 93 system shown in FIG. 4 or an end cup system not shown. A preload is applied to the ball 8 by slightly shifting the phase of the screw groove 91 on the ball nut 9 side with respect to the screw groove 11 on the ball screw shaft 7 side. That is, the screw grooves 11 formed on the ball screw shaft 7 are provided at a predetermined pitch over the entire length, whereas the screw groove 91 on the ball nut 9 side has the phases of the left and right screw grooves with the center as a boundary. Preload is applied to the balls 8 by narrowing them toward the center or expanding them on both ends. In this example, the contact angle lines X _{1 to} X _{4 of the} balls 8, ...
Is inclined toward the center of the ball screw shaft 7 in the direction of opening toward the end.

Here, the ball spline shaft 13 will be described in detail. The fixed end portion 131 fixed to the fixed bed 2 is fitted into the shaft hole 141 formed in the fixed bracket 14, and the end portion thereof is axially moved by the snap ring 132. It is fixed to. On the other hand, between the fixed end 131 and the shaft hole 141 of the fixed bracket 14, the key 133
It is fixed in the direction of rotation by. A ring-shaped stopper 21 is attached to the upper end surface of the fixing bracket 14 by a bolt.
The ball screw shaft 7 is integrally fixed by the stopper 22, and the downward movement of the ball screw shaft 7 is restricted by the stopper 21.

On the other hand, the upper end of the ball spline shaft 13 is located at a position slightly lower than the upper end of the ball screw shaft 7 at the lower limit position of the table 4 so as not to interfere with the table 4. An upper limit stopper 63 for restricting upward movement is attached to the upper end of the ball screw shaft 7. The upper limit stopper 23 is a disk-shaped member having a diameter larger than the shaft diameter of the ball spline shaft 13, and is fixed to the shaft end with a bolt 24.
A portion of the ball spline shaft 13 which projects outward from the outer periphery of the ball spline shaft 13 is engaged with the spline nut 15 to restrict upward movement of the table 4. Therefore, the moving range of the table 4 is the length between the upper end of the spline nut 15 and the upper limit stopper 23 at the lower limit position of the table 4.

The spline nut 15 has a fixing flange 151 at its lower end.
Of the ball screw shaft 7, the ball nut 9 is fitted into the hollow hole 10 of the ball screw shaft 7 so that the fixing flange 151 is engaged with the lower end surface of the ball screw shaft 7. The shaft 7 is integrally fixed.

In the ball spline shaft 13, for example, three portions 134 as shown in FIG. 7 are formed so as to project in three positions in the circumferential direction,
Spline grooves 135 are formed on both side surfaces of each of the portions 134, respectively. On the other hand, on the inner circumference of the spline nut 15,
One pair of jetty 153,153 so as to sandwich both sides of each part 134
Are provided, and spline grooves 154, ... Are provided at respective portions of each jetty 153, ...
… Is intervening. The contact direction of each ball 28 with the spline grooves 135, 154 is an angular contact type having an angle with the radial direction.

The spline groove 135.154 is precisely ground into an R shape close to the ball diameter. Further, each ball 28 is preloaded in the rotational direction to increase its rigidity, and the angular lash is made zero.

In addition, each ball 28 is held by a retainer 25 incorporated in the inner periphery of the spline nut 15 so as to make an aligned circulation movement.

The servomotor 16 is composed of a rotor 19 as a cylindrical rotating portion whose upper end is closed, and a stator 18 as a non-rotating portion located inside the hollow of the rotor 19. The stator 18 is attached to the upper end of a support bracket 162 fixed to the fixed bed 2 by bolts 161, and the rotor 19 is attached to the support bracket 162 by a cross roller bearing 20.
It is rotatably supported via. The cross roller bearing 20 has a large number of rollers 203 interposed between an inner ring 201 and an outer ring 202, and the axes of the rollers 203, ...
They are arranged to have a tolerance of 90 degrees. The inner ring 201 is fixed to the support bracket 162, and the outer ring 202 is fixed to the inner circumference of the rotor 19.

Further, the servo motor 16 is provided with an annular light-shielding plate 30 in which marks (not shown) are attached to the rotor 19 at a predetermined pitch in the circumferential direction, as shown in FIG. An encoder 32 for optically detecting is provided.

The outer cover 6 is provided with a power connector 33 and an output connector 34 from the encoder 32. Each connector 33, 34 is connected to the control unit 35.

In the lift table configured as described above, after the work is supported on the table 4, the servo motor 16 is driven to rotate the ball nut 9 that is screwed onto the ball screw shaft 7 to move the table 4 up and down. Do.

Here, the control is performed by sending an operation signal from the control unit 35 to the servo motor 16 to drive the servo motor 16 to rotate the ball nut 9, and at the same time, a predetermined signal is given by a signal of an encoder incorporated in the servo motor 16. The rotation angle is detected, and the table 4 is vertically positioned based on the screw pitch of the ball screw shaft 7 and the rotation angle. Positioning in this case can be performed with high accuracy by a signal from the encoder.

In particular, when the ball nut 9 is started and stopped or when the ball screw 9 is switched between forward and reverse rotation, a force is applied to rotate the ball screw shaft 7. However, the balls 28, ... Interposed between the ball spline shaft 13 and the spline nut 15, The angular contact structure prevents backlash in the rotation direction.

Further, since the balls 8, ... Interposed between the ball screw shaft 7 and the ball nut 9 are also preloaded, rattling of the ball screw shaft 7 in the axial direction is prevented, and the servo motor 16 described above is used. In combination with precise drive control, extremely precise positioning can be performed.

Considering the case where a moment load acts on the ball screw shaft 7, for example, when a clockwise moment in the figure acts, this moment is taken up by the ball nut 9 and the spline nut 15.
High support rigidity.

(Effects of the Invention) The present invention has the above-described configuration and action, and is configured so that a spline shaft that holds a screw shaft in the axial direction and is fixed in the rotation direction is inserted into a hollow hole of the screw shaft. Therefore, as compared with the case where the spline groove is formed at one end of the screw shaft, the length of the screw shaft for ensuring the same amount of elevation can be shortened, and the device can be downsized.

Further, since the screw shaft is doubly supported on the inner side and the outer side by the nut screwed on the outer peripheral side thereof and the spline shaft engaged with the inner peripheral side thereof, it is possible to enhance the support rigidity against moment load.

Furthermore, since the rotating part of the rotary drive source is directly connected to the nut,
As in the conventional case, the transmission mechanism is not required, so that the positioning accuracy can be improved and the operation response can be improved.

[Brief description of drawings]

1 is a vertical sectional view of a lift table according to an embodiment of the present invention, FIG. 2 is a plan view of the apparatus of FIG. 1, and FIG. 3 is a vertical sectional view of the apparatus of FIG. 4 is a longitudinal sectional view of the ball screw shaft of FIG. 1, FIG. 5 is a front view of the ball spline shaft of FIG. 1, and FIG. 6 is a spline nut engaging with the ball spline shaft of FIG. FIG. 7 is a longitudinal sectional view, FIG. 7 is a lateral sectional view of the spline nut of FIG. 6, and FIG. 8 is a partial sectional view showing an example of the encoder. Explanation of symbols 1 …… Lift table 2 …… Fixed bed 3 …… Screw feed mechanism 4 …… Table 7 …… Ball screw shaft, 8 …… Ball 9 …… Ball nut, 91 …… Screw groove 10 …… Hollow hole, 11 …… Screw groove 13 …… Ball spline shaft 15 …… Spline nut 16 …… Servo motor (rotational drive source) 18 …… Stator, 19 …… Rotor 20 …… Cross roller bearing 21 …… Stopper, 23 …… Upper limit stopper 25 …… Cage, 28 …… Ball 32 …… Encoder

Claims (5)

[Claims] 1. A screw shaft for vertically moving a table supported on a fixed bed via a screw feed mechanism, the screw feed mechanism extending in the vertical direction and having its upper end fixed to the table, and the screw shaft. A nut that is screwed together and rotatably attached to the fixed bed side and is operatively connected to a rotary drive source; and a hollow hole whose lower end opens at the screw shaft, and the fixed bed. A spline shaft that can be inserted in the hollow hole of the screw shaft so as to be movable in the axial direction is fixed, and the spline shaft is axially movable in the inner circumference of the hollow hole of the ball screw shaft and is fixed in the rotational direction. A lift table comprising a bearing portion, a non-rotating portion of the rotary drive source being fixed to a fixed bed, and the rotating portion being directly connected to a nut. 2. The lift table according to claim 1, wherein the spline shaft and the bearing portion are fitted via balls. 3. The lift table according to claim 2, wherein the ball according to claim 2 is an angular contact with a spline groove formed in the spline shaft and the bearing portion. 4. The lift table according to claim 1, 2 or 3, wherein a large number of balls are interposed between the screw shaft and the nut. 5. The lift table according to claim 4, wherein the balls interposed between the screw shaft and the nut are preloaded by shifting the phases of the screw grooves on the nut side and the screw shaft side.